Hard disk drives offer a convenient, efficient, and cost effective way to store vast amounts of digital data used by virtually every computer system ranging from mainframes, workstations, and desktop personal computers to portable laptop computers. Basically, data is stored magnetically as a series of magnetic transitions representing bit strings consisting of "1's" and "0's." One or more transducers are used to write the data onto the surfaces of spinning, magnetically coated disks. The data is written to a number of circular, concentric "tracks." Later, the pre-recorded data is read back from the tracks by detecting changes in the polarities of the magnetic domains representing the bits of data.
A servo controller is used to control an actuator for physically positioning the transducer over the correct track of the disk during the read/write process. The act of moving the transducer to the desired location is known as a "seek"operation. Servo information, used to provide position feedback to the servo controller, is recorded onto the disks at specific, pre-defined locations. In a preferred embedded servo system each track has a plurality of equally spaced apart servo sectors or "wedges" containing the servo information. This servo information is read during the seek operation to help guide the servo system to the correct track and to provide the requisite timing synchronization. Once the correct track is located, servo "bursts" recorded onto the disks are used to make minor adjustments to the actuator so that the transducer properly follows the track.
Unfortunately, there are many factors which may cause a servo error. One reason for servo errors relates to the fact that the servo data residing in the servo sectors is read back as electrical signals in the form of pulses by the transducer. The level of the readback pulses are typically so low that they are highly susceptible to becoming distorted. The electrical pulses may be corrupted by noise or by other external signal sources. The servo data is usually conditioned by a read channel integrated circuit chip, which provides signal conditioning circuitry controlled programatically by setting parameters in registers within the chip. Conventionally a standard or "default" set of parameters, developed during the design of disk drive, is applied during the reading of servo sectors. Because the head and media characteristics varies from surface to surface and drive to drive in a mass production process, the signals produced by the head and presented to the read channel may result in the default parameters being sub-optimal, causing rejection of a disk drive. In order to achieve high quality, each individual hard disk drive must be tested thoroughly in order to ensure that its servo system works properly and is reliable.
Thus, there is a need for some method and apparatus which could automatically determine the optimal parameters for tuning the servo systems of hard disk drives so as to minimize servo errors. The present invention provides such a solution.